Nowadays, oil tankers represent 25% of the targets of maritime piracy attacks. The main goal of this paper is to propose an approach to evaluate the vulnerability of the maritime supply chain to piracy risk. This approach, based on spatial reasoning and modelling tend to measure the impact of piracy on the network by the changes on maritime network realized by disruptions. To achieve it, we use multi-agent system, which can be defined by a set of agent within a shared environment. Agents are entity which has their own goal, capacity and resources which induce a specific behavior. By using the sum of these behaviors, the main objective of this paper is to measure disruptions by a conceptual approach to qualify and quantify the piracy risk.